Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Total property revenues	$ 342,417	$ 341,974	$ 336,766	$ 333,168	$ 326,905	$ 327,078	$ 319,562	$ 312,178	$ 1,354,325	$ 1,285,723	$ 1,185,498
Net income	109,662	85,035	75,795	187,551	204,517	70,162	76,824	86,907	458,043	438,410	248,239
Net income available to common stockholders	$ 103,613	$ 79,723	$ 70,759	$ 178,964	$ 195,569	$ 65,561	$ 72,013	$ 77,981	$ 433,059	$ 411,124	$ 226,865
Net income:
Net income available to common stockholders - basic (in dollars per share)	$ 1.57	$ 1.21	$ 1.08	$ 2.73	$ 2.98	$ 1.00	$ 1.10	$ 1.19	$ 6.58	$ 6.28	$ 3.50
Net income available to common stockholders - diluted (in dollars per share)	1.57	1.21	1.08	2.72	2.98	1.00	1.10	1.19	$ 6.57	$ 6.27	$ 3.49
Market price:
High (in dollars per share)	264.07	270.04	268.97	238.57	234.07	236.56	237.50	240.55
Low (in dollars per share)	237.33	249.46	229.14	218.41	200.01	217.16	207.20	191.25
Close (in dollars per share)	241.37	254.03	257.27	231.53	232.50	222.70	228.09	233.86
Dividends declared (in dollars per share)	$ 1.75	$ 1.75	$ 1.75	$ 1.75	$ 1.6	$ 1.60	$ 1.60	$ 1.60
Essex Portfolio, L.P. [Member]
Condensed Income Statements, Captions [Line Items]
Total property revenues	$ 342,417	$ 341,974	$ 336,766	$ 333,168	$ 326,905	$ 327,078	$ 319,562	$ 312,178	$ 1,354,325	$ 1,285,723	$ 1,185,498
Net income	109,662	85,035	75,795	187,551	204,517	70,162	76,824	86,907	458,043	438,410	248,239
Net income available to common stockholders	$ 107,149	$ 82,444	$ 73,181	$ 185,110	$ 202,201	$ 67,784	$ 74,463	$ 80,765	$ 447,884	$ 425,213	$ 234,689
Net income:
Net income available to common stockholders - basic (in dollars per share)	$ 1.57	$ 1.21	$ 1.08	$ 2.73	$ 2.98	$ 1.00	$ 1.10	$ 1.19	$ 6.58	$ 6.28	$ 3.50
Net income available to common stockholders - diluted (in dollars per share)	1.57	1.21	1.08	2.72	2.98	1.00	1.10	1.19	$ 6.57	$ 6.27	$ 3.49
Market price:
Dividends declared (in dollars per share)	$ 1.75	$ 1.75	$ 1.75	$ 1.75	$ 1.6	$ 1.6	$ 1.6	$ 1.6